It's not quite clear to me how this particular skill works. Having gone 2/2 with it on my dk during beta I noted that it did not increase my damage at all when using class skills searing strike and fiery breath(neither on the tool tip nor in combat). Is there a burning proc that is random when you use these abilities or does the +66% bonus apply to ablities afterburn, or is it just bugged? Thanks

Searing strike and fiery breath cause flame damage, not burning. Burning is a fire condition that has a random chance to proc whenever hitting someone with a fire attack.

Basically what Mikemad97 said. It only works on the "burning" effect that can proc off of any fire damage ability.